Many exotic metals, such as titanium, cannot be welded in the presence of air without producing a weak and discolored weld. An inert gas such as argon or helium may be used to displace the air surrounding the weld, thereby solving the problem. A popular solution is to place the workpieces to be welded into a welding chamber that has been designed to purge the air and replace it with inert gas.
There are currently on the market several types of welding chambers suitable for welding exotic metals in an inert-gas atmosphere. Each provides access to workpieces and a welding torch with plastic gloves through portholes in the side of the chamber. Each has a system for introducing the inert gas to the interior of the chamber. Each provides a vent in the chamber to expel air.
A “beach-ball” type of welding chamber is made from flexible clear-plastic pieces fastened together in the shape of a flat-bottomed beach ball. U.S. Pat. No. 5,685,771 to Kleppen on Nov. 11, 1997 is an example of such a device. This type of device is usually mounted to a round work table. Workpieces to be welded may be inserted and removed through a zipper in the plastic. A major problem with the beach-ball type of chamber is its susceptibility to damage from a hot torch, from weld spatter, or from sharp-edged workpieces, any of which may cause holes that allow the escape of inert gas or the entry of air. Costly downtime is the result until the damaged area is patched. Secondly, rips in the plastic may occur in the creases caused by repeated inflations and deflations. Thirdly, pockets of air residing the in the folds of such a chamber when deflated can mix with incoming inert gas, increasing the time required to fully purge such a chamber. Lastly, it is difficult to clean such a soft plastic chamber without it becoming scratched, which impedes viewing therethrough during subsequent operation by a user.
A “glove-box” or “sand-blaster” type of chamber is a steel box with gloved portholes in front and a clear plastic viewing window above the portholes. Workpieces are inserted and removed through a door in the top or side of the box. One problem with this type of device is its limited visibility through what is typically a small window. Secondly, if the door is located on the top of the chamber, it is difficult to add or remove workpieces, if the door is on the side of the chamber, inert gas is lost when the chamber is opened. Thirdly, the inside square edges and corners can trap pockets of air, increasing purge time and making cleaning relatively difficult.
A “bell-jar” type of chamber consists of a rigid plastic dome resting on a heavy steel table. A substantial counter-weight arrangement is necessary to help left the heavy dome. Porthole gloves are mounted through the plastic dome. This 50-year-old design is attributed to the aerospace industry in the early years of titanium welding and has little or no prior art. Workpieces are placed on or removed from the table by lifting the dome, resulting in a complete loss of gas. Although an optional access chamber may be built into the side of the dome to allow small workpieces to be inserted or removed from the chamber without lifting the dome, such as access chamber requires a separate purge system from the main bell-jar chamber. Often called the “Cadillac” of welding chambers, this type of device has several drawbacks. First is the expense, as many companies find such a device cost-prohibitive. Secondly is the often impractical weight of such a device. A forklift truck is typically necessary to move such a device. Thirdly, the right-angle juncture of the dome and the table leaves pockets of air. The device uses a diffuser to slow the entry of gas to prevent any turbulence, thereby inhibiting any scrubbing action of residual pockets of air within the device, resulting in longer purge times.
Accordingly, there is a need for an affordable welding chamber that allows for unfettered access to 100% of the chamber while still minimizing the escape of heavier-than-air gas from the chamber when a workpiece is removed or introduced to the chamber. Such a needed device would thereby conserve the inert gas that fills the chamber during welding operations. Further, such a needed device would provide a full 100% visibility of the inside of the chamber when a user is operating the device, such as through use of a pair of glove ports. Such a needed device would facilitate electrical grounding of any metal workpieces for arc welding thereof. Still further, such a needed device would be relatively light weight, easy and compact to store, easy to clean and free from any sharp projections or corners either inside the chamber or on the exterior surface thereof. Still further, the gas inside the chamber of such a needed device could be quickly purge if desired, minimizing turn-around time between welding sessions requiring a different gas inside the chamber. The present invention accomplishes these objectives. Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.